The typical escalator, as is well known, comprises a closed loop arrangement of interconnected stairs or steps which are propelled between floors, thereby providing a moving staircase, in effect, upon which passengers stand in order to be transported between the floors. The drive mechanism typically comprises a chain which is driven by electric motors. The stairs are connected to this chain which pulls the stairs on tracks that extend between the floors. The relative orientation of the tracks with respect to each other and the floors determines the position of the stairs. This track orientation is used to create the staircase arrangement that the passengers stand on in moving between the floors and to orient the stairs so that they return from the floor concealed below the staircase portion. Another similar conveyance system does not use staircases, but rather a continuous, flexible belt, somewhat like a conveyor, for transporting the passengers between the floors. That system is somewhat like an incline conveyor belt or ramp. A major difference between this ramp system and the traditional escalator system is that the ramp system takes up considerably more space because it must be inclined so as to enable passengers to stand on it comfortably, while the traditional escalator system accomplishes that result by providing the horizontally oriented stairs that they may stand upon when being transported.
Both systems, however, suffer the same common disadvantage: only 50% of the transporting surface area in the overall system is available at any time for transporting passengers. Up and down going passenger loads are not used to offset each other; this unduly wastes energy.